I have a question about the wall-reflection term when using the Reynolds Stress models RSM .

When simulating turbulent flow in complex geometry with the RSM, a wall-reflection correction is needed for the pressure-strain term. There is a parameter △y,denoting the normal distance to the wall. I am confused that when there are several walls in the geometry, how many wall-reflection terms will be? Does every wall corresponds a wall-reflection term? For example ,when I calculate the turbulent flow past a backward-facing step, how do I calculate the wall-reflection term near the step corner?